Crystal-size effect on the kinetics of CO2 adsorption in metal organic frameworks studied by NMR

Abstract

We study the dynamics and the exchange of carbon dioxide (CO₂) adsorbed in a metal organic framework (MOF) by ¹³C NMR for various sizes of the host crystal ranging from micrometers to millimeters. We found that the guest CO₂ molecules adsorbed in [Zn₂(1,4-NDC)₂(dabco)]_n MOF undergo exchange at a rate that depends on the size of the host crystal, revealing that the smaller the host crystals are, the faster the exchange becomes. Such a trend can be explained by the size-dependent surface-to-volume ratio.